+47.64754, -122.34736
47°38'51" N, 122°20'50" W


Source: National Bridge Inventory. Information not verified; use at your own risk.
Name:SR 99 over LAKE UNION
Structure number:0001447A0000000
Location:7.7 N JCT SR 509
Purpose:Carries highway and pedestrian walkway over highway, waterway, and railroad
Route classification:Principal Arterial - Other Freeways or Expressways (Urban) [12]
Length of largest span:799.9 ft. [243.8 m]
Total length:2955.2 ft. [900.7 m]
Roadway width between curbs:56.4 ft. [17.2 m]
Deck width edge-to-edge:69.6 ft. [21.2 m]
Vertical clearance below bridge:134.8 ft. [41.1 m]
Owner:State Highway Agency [01]
Year built:1931
Historic significance:Bridge is on the National Register of Historic Places [1]
Design load:M 18 / H 20 [4]
Number of main spans:8
Main spans material:Steel [3]
Main spans design:Truss - Deck [09]
Deck type:Concrete Cast-in-Place [1]
Wearing surface:Bituminous [6]

Latest Available Inspection: August 2017

Good/Fair/Poor Condition:Fair
Status:Open, no restriction [A]
Average daily traffic:58,319 [as of 2012]
Truck traffic:3% of total traffic
Deck condition:Satisfactory [6 out of 9]
Superstructure condition:Fair [5 out of 9]
Substructure condition:Satisfactory [6 out of 9]
Structural appraisal:Somewhat better than minimum adequacy to tolerate being left in place as is [5]
Deck geometry appraisal:Basically intolerable requiring high priority of replacement [2]
Underclearances appraisal:Somewhat better than minimum adequacy to tolerate being left in place as is [5]
Water adequacy appraisal:Equal to present desirable criteria [8]
Roadway alignment appraisal:Equal to present desirable criteria [8]
Channel protection:Banks are protected or well vegetated. River control devices such as spur dikes and embankment protection are not required or are in a stable condition. [8]
Pier/abutment protection:Navigation protection not required [1]
Scour condition:Bridge foundations determined to be stable for the assessed or calculated scour condition. [8]
Operating rating:40.9 tons [37.2 metric tons]
Inventory rating:24.0 tons [21.8 metric tons]
Sufficiency rating:46.9
Recommended work:Bridge rehabilitation because of general structure deterioration or inadequate strength. [35]
Estimated cost of work:$69,738,000

Previous Inspections

DateSuff. RatingConditionDeckSuperstructureSubstructureSD/FOADT
August 201746.9FairSatisfactoryFairSatisfactoryFO58319
August 201546.5FairSatisfactoryFairSatisfactoryFO58319
August 201346.5FairSatisfactoryFairSatisfactoryFO58319
August 201144.4FairSatisfactoryFairSatisfactoryFO69463
December 200944.1FairSatisfactorySatisfactoryFairFO71085
June 200755.2FairSatisfactorySatisfactorySatisfactoryFO73836
May 200553.2FairSatisfactorySatisfactorySatisfactoryFO73836
July 200353.2FairSatisfactorySatisfactorySatisfactoryFO73836
March 200153.2FairSatisfactorySatisfactorySatisfactoryFO73836
June 199953.2FairSatisfactorySatisfactorySatisfactoryFO73836
May 199759.3FairSatisfactorySatisfactorySatisfactoryFO73836
May 199527.9PoorSatisfactoryPoorSatisfactorySD73836
June 199329.3PoorSatisfactoryPoorSatisfactorySD59363
January 199227.8PoorFairPoorSatisfactorySD59363

Element Data

Source: National Bridge Elements dataset, 2016 edition. This feature is experimental.
ElementUnitsQuantity1. Good2. Fair3. Poor4. Serious
Reinforced Concrete Girder/Beamlinear ft.1,6821,674350
Steel Stringerlinear ft.35,92135,8690520
Steel Protective Coatingsq. ft.427,4010426,5460855
Reinforced Concrete Stringerlinear ft.2,5232,521020
Reinforced Concrete Decksq. ft.166,957166,9300027
Wearing Surfacessq. ft.166,9570166,883722
Steel Trusslinear ft.4,2222,697251,5000
Steel Protective Coatingsq. ft.502,3490501,34401,005
Steel Floor Beamlinear ft.5,9005,8680320
Steel Protective Coatingsq. ft.70,200070,0600140
Reinforced Concrete Floor Beamlinear ft.3,0003,000000
Steel Pin or Pin & Hangar Assemblyeach28180010
Steel Gusset Plateeach438438000
Steel Columneach44000
Steel Protective Coatingsq. ft.4704700
Reinforced Concrete Columneach3826390
Reinforced Concrete Abutmentlinear ft.139139000
Reinforced Concrete Pileeach22000
Reinforced Concrete Pier Caplinear ft.3503380120
Strip Seal Jointlinear ft.171017100
Open Jointlinear ft.4,3320004,332
Assembly without Seal Jointlinear ft.684040322556
Movable Bearingeach22000
Fixed Bearingeach106040
Other Bearingeach1414000
Bridge Rail
Steel or Aluminum Bridge Raillinear ft.5,9105,8140960
Reinforced Concrete Bridge Raillinear ft.5,9105,910000